Organic vapor jet printing is a known technique for the deposition of organic materials onto a substrate. It can be used to produce organic light emitting diodes (OLEDs) and other eletro-phosphorescent devices, as well as photo-responsive devices such as organic phototransistors, organic photovoltaic cells, and organic photodetectors. Pixel dimensions on the order of microns are achievable using known techniques—see, for example, U.S. Patent Application Publication Nos. 2010/0245479A1 and 2010/0247766A1, both published Sep. 30, 2010. The complete contents of these published applications are hereby incorporated by reference. To achieve such pixel densities, accurate positioning of the print head within a few microns of the substrate is desirable.